Numerical Research on Wave-making Resistance of Trimaran

A 3D rankine panel method was developed for calculating the linear wave-making resistance of a tri-maran with Wigley hulls. In order to calculate the normal vector and derivative of the body surface accurately, non-uniform rational B-spline (NURBS) was adopted to represent body surface and rankine source density. The radiation condition is satisfied using the numerical technology of staggered grids. Numerical results show that the linear wave-making resistance of the trimaran can be calculated effectively using this method.

Grid convergence study in the resistance calculation of a trimaran

As a new type of hull form,trimaran has remarkable excellent performances and has drawn more and more attention.When the viscous CFD technology now available is applied to the research of resistance performance of trimaran,the spatial discretization would usually result in the grid error and uncertainty,and thus the considerable discrepancy between the numerical results and the experimental data.In order to ascertain how much the grid would affect the calculation,the grid convergence should be studied.A mathematical trimaran was chosen as an example,with the commercial code CFX for the simulation,VOF for surface treatment,and the grid study was carried out based on two different turbulence models.It was concluded that carrying out grid study is helpful in estimating the grid error and uncertainty,and indicating the direction of improving the credibility of the numerical calculation, and,in addition to grid errors and uncertainties,the turbulence modeling errors and uncertainties contribute to the simulation errors.

Tank Tests with a Scaled Model of a BOC-50 Sailing Yacht Model in Calm Water and in Regular and Random Head Waves

In this paper the performance of a BOC-50＇ sailing yacht model in calm water and in realistic sea states is investigated experimentally. A scaled model of the hull form with the keel-bulb configuration has been tested in the towing tank of the LSMH of NTUA. During the tests the calm water resistance and the dynamic responses, including the added resistance in waves were recorded. Results referring to the resistance, the side force, the CG displacement, the pitch as well as the vertical accelerations of the model at the bow, the CG and the stern are presented. Moreover, by using a Velocity Prediction Program the polar and the stability diagram of the tested sailing yacht were calculated. Useful conclusions about the dynamic behavior of the model were obtained.

Analysis of the Motive for the Use of LNG-Powered Ships in the Inland Waters of Yangtze River

The fuels that hardly pollute water body and atmospheric environment during burning are regarded as clean fuels. Liquefied Petroleum Gas （LPG）, Compressed Natural Gas （CNG） and Liquefied Natural Gas （LNG） are three representative clean fuels that are widely used in the shipping industry. From both ecological and economic point of view, LNG is treated as the best fuels in shipping industry by the ship-owners and Chinese government. In this paper, the wide applications of LNG-powered ships are analyzed from three aspects, including the global energy source structure, economic demands and the formulation of international conventions. Also, the functions of relevant domestic policies on how to accelerate LNG-powered ships widely used in inland waters of Yangtze river, China are summarized. At last, the reasons of the use of LNG-powered ships in inland waters of China in recent years under the impulsion of various factors are discussed in the end.

Reconstruction of plasmoid and traveling compression region in the near-Earth magnetotail

Cluster spacecraft observed an earthward flowing plasmoid along with a travelling compression region （TCR） structure in southern plasma sheet boundary layer （PSBL） at 21：09 UT of September 19, 2001. We have reconstructed the two-dimensional topology of the magnetic field structure observed by C1 using Grad-Shafranov reconstruction method. Results show that CI passed through part of a plasmoid, which compressed the lobe magnetic field and formed a TCR. The size of the whole plas- moid structure in X direction is estimated to be about 3 Re. Furthermore, using multi-spacecraft observations, we have found some detailed information about this structure. First, C1 observed bi-streaming electron components, which supports our sug- gestion that the spacecraft passed through closed field lines. Second, a small magnetic field perturbation within this plasmoid accompanied by slight decrease in electron flux suggests that a flux rope core might exist at the center of the plasmoid.